some will bash Harbor Freights trailers for a build platform. I built my 1st offroad trailer from the harbor Freight Super Duty trailer. I scrap the tongue & fabricated my own tongue w\2" back bone. I chopped the frame down to 40 1\2" wide x 6ft long, bolted the frame together (squared it up) then welded up "all" the joints. The reason why I chopped the frame down to the size is the tub kit required a chassis that was 40 1\2" x 72". The tub kit I used was Dinoot M Series w\ CJ tailgate. I scrapped the original slipper spring type suspension & went with Scott Chaney's Smooth Ride Kit & order shocks & shock mounts.
After all the fabrication & welding done I sand blasted the original red enamel paint off & primed with PPG's Automotive Epoxy Primer, followed by 3 coats of PPG's Omni Blasé pant in Cerakotes Coyote Tan, & 3 coats of PPG Automotive Gloss Clear w\ Flattner added to Satin Finish. Done right with some welding the Harbor Freight or Northern Tool trailers can make for a great offroad build plateform. The wife & I put a lot of miles of offroad trails & roads on this trailer with several years of use & memories made w\o any structural issues. When I sold the trailer last year it's still running trails & dirt roads strong in NW Arkansas in the Ozarks.